In the field of lighting, and in view of the advantages of smaller size, more preferable price, and wider dimming range, silicon-controlled rectifier (SCR) dimming schemes are widely used. For example, applications include stage lighting, directional lighting, and surrounding illumination. By controlling a conduction phase angle of an SCR element, a part of the input sine wave of an AC power supply may be cut off to decrease average voltage value to control the supply to the lamp load, thus achieving dimming operation.
In cases when the external voltage supply is relatively low, a holding resistor may be added to generate a current to maintain conduction of the SCR element. However, drawbacks of this approach include increased power loss, lower operation efficiency, and poorer dimming performance.